<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .content {
            width: 800px;
        }

        .content>div {
            float: left;
            width: 100px;
            height: 100px;

        }

        .content .one {
            width: 100%;
            background-color: grey;
        }

        .left {
            background: red;
        }

        .center {
            background: green;
        }

        .right {
            background-color: blue;
        }
    </style>
</head>

<body>

    <div class="content">
        <div class="one">one</div>
        <div class="left">left</div>
        <div class="center">center</div>
        <div class="right">right</div>
    </div>
</body>

</html>